Axial compressor blades in a gas turbine engine are typically arranged in an annular array to rotate within the gas path bounded by an outer shroud and an inner platform. The surface defined by the rotating blade tip and the adjacent shroud surface are closely matched, preferably with a minimal gap. Leakage between the blade tips and the shroud may result in a reduced efficiency for the compressor. Further, the passage of the blade tip relative to the shroud usually results in the formation of vortices which may reduce compressor efficiency due to the turbulent air flow.
Compressor blades are relatively thin structures that are subjected to forces due to the air flow over the blade surfaces and due to engine vibration. The configuration of the material mass in a blade results in fundamental vibratory modes. When the frequency of oscillations in load application during engine operation equals one of the blade's fundamental vibratory modes, higher stresses are experienced by the blade.
Since turbine engines intake air that can contain foreign objects, such as birds, blades must be capable of withstanding impact from foreign objects that can be ingested into the engine.